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An experiment was set up to determine the movement of molecules through a dialysis-tubing bag into water. A dialysis-tubing bag containing 5\(\%\) lactose and 5\(\%\) fructose was placed in a beaker of distilled water, as illustrated. After four hours, fructose is detected in the distilled water outside of the dialysis-tubing bag, but lactose is not. What conclusions can be made about the movement of molecules in this experiment? a. Fructose, being a monosaccharide, diffused through the dialysis bag into the distilled water. However, lactose, being a disaccharide, could not diffuse through the dialysis bag. b. Fructose was homogenized by lactose, allowing and into the distilled water. Lactose is not homogenized, so it could not pass through the dialysis bag. c. Fructose and lactose are oppositely charged and separated out due to the force of repulsion. d. Fructose diffused because of the pore specificity of the semipermeable membrane, not because of its concentration gradient.

Step by step solution

01

Understand the Problem Statement

Identify the molecules involved and their behavior during the experiment. The problem involves a dialysis-tubing bag containing 5% lactose and 5% fructose placed in distilled water. After four hours, fructose is detected outside the bag, while lactose is not.

02

Identify Properties of Molecules

Recognize that fructose is a monosaccharide (a simple sugar), while lactose is a disaccharide (composed of two monosaccharides). Mono- and disaccharides have different physical and chemical properties, including size.

03

Determine Diffusion Mechanism

Evaluate why fructose moved through the dialysis bag and why lactose did not. Dialysis tubing acts as a semipermeable membrane, which allows smaller molecules like monosaccharides to pass through while restricting larger molecules like disaccharides.

04

Evaluate Given Options

Review each conclusion option: a. Correct - Fructose diffused through the bag due to its small size. Lactose could not diffuse because it is larger. b. Incorrect - The concept of homogenization by lactose and diffusion is not biologically relevant. c. Incorrect - Fructose and lactose are not charged molecules that would repel each other. d. Incorrect - Diffusion for fructose occurred due to its size, not membrane pore specificity or concentration gradient.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Monosaccharides and Disaccharides

Monosaccharides and disaccharides are types of carbohydrates. Carbohydrates are vital sources of energy. Monosaccharides are the simplest form of carbohydrates with a single sugar molecule. Common examples include glucose and fructose. These simple sugars are small and can easily pass through membranes.
Disaccharides, on the other hand, are composed of two monosaccharide molecules linked together. Examples include lactose (made of glucose and galactose) and sucrose (made of glucose and fructose). Because they are larger, disaccharides encounter more difficulty passing through membranes compared to monosaccharides.

Semipermeable Membrane

A semipermeable membrane is crucial in biological systems. This type of membrane allows certain molecules to pass through while blocking others. For instance, dialysis tubing is a type of semipermeable membrane often used in experiments to simulate the cell membrane.
The selectivity of these membranes depends on factors like the size of the molecule and membrane pore size. In our experiment, the dialysis tubing allowed fructose (a smaller monosaccharide) to diffuse into the water but restricted lactose (a larger disaccharide). This mechanism helps simulate and understand cellular processes, including nutrient absorption and waste removal.

Diffusion Mechanism

Diffusion is a process where molecules move from an area of higher concentration to an area of lower concentration, aiming to reach equilibrium. It is crucial in numerous biological functions, such as gas exchange in the lungs and nutrient absorption in cells.
In the dialysis experiment, diffusion facilitated the movement of fructose from inside the bag to the surrounding distilled water. Because fructose is small enough, it diffused through the pores of the semipermeable membrane. Lactose, owing to its larger size, couldn't pass through, hence remained inside the bag. This example demonstrates how molecule size and membrane selectivity are central to the diffusion process.